For a potential "everyday use" cryptocurrency that dominates the global economy, I think some rate of inflation/emission is 100% necessary.
But I don't think Grin is trying to be that with the way everything else is situated. The elimination of denominations and addresses makes this currency fundamentally difficult to interact with. I also think an inherently private coin would be incompatible with the role of worldwide day-to-day use.
I don't see any other situation for Grin or any crypto where unlimited supply is a good thing to have. What's the justification?
regarding being unlimited...
compare it to gold, technically you can claim gold is limited but thousands of years back and today we are still mining it, in the future we still are going to mine it, although limited it feels like it is unlimited. we may even mine it outside the earth in the future if we go inter stellar/inter planetary.
if we say that we will mine gold in the whole universe, or just say in our galaxy..what would we say? "that's unlimited"
well we haven't even explored the earth's crust or the earth's mantle and scour the ocean floors for gold mining.